1. Field of the Invention
The present invention relates to a fuel injection controller for controlling an injection operation of an injector, which injects and supplies fuel to be used for combustion in an engine, and a diagnosis method of a fuel supply system of an engine including an injector for diagnosing whether or not the fuel supply system operates normally.
2. Description of Related Art
As well known, for example, an internal combustion engine used as a power source of an automobile or the like ignites and burns fuel injected and supplied from an injector to produce output torque. A diesel engine for an automobile or the like recently adopts an injection system, which is a so-called multiple injection system, of performing a sub-injection with an injection quantity smaller than a main injection before or after performing the main injection, which produces output torque during one combustion cycle. For example, today noises or an increase of a NOx emission quantity at the time of fuel combustion is seen as a problem. For solving this problem, there is a case of performing a pre-injection or a pilot injection with a small quantity of fuel before the main injection. In addition, there is a case where even after the main injection, for the purpose of activation of diffusion combustion or reduction in emission of particulate matter (PM), an after-injection is performed at injection timing close to that of the main injection. Further, there is a case where for the purpose of a rise of an exhaust gas temperature, activation of a catalyst by reduction constituent supply or the like, a post-injection is performed at injection timing retarded significantly from that of the main injection. A recent engine control adopts one or an arbitrary combination of these various injections to perform supply of fuel to the engine in an injection mode (injection pattern) more suitable for various situations.
Conventionally, there is widely used a fuel injection controller for controlling an injection operation of an injector to perform a multiple injection. This controller uses a map in which an injection pattern (adapted value) for each engine operating condition is written or a mathematical expression thereof to set an injection pattern in accordance with an engine operating condition at each time. This controller holds an optimal pattern (adapted value) obtained by experiments or the like concerning each engine operating condition assumed beforehand as the map or the mathematical expression (for example, stored and held in a ROM). This controller refers to the map or the mathematical expression and thereby sets an injection pattern in accordance with an engine operating condition. Besides, like a controller described in Patent Document 1 (JP-A-2005-264810), there is proposed a controller of changing an injection pattern by monitoring an engine operating condition.
Such use of the map in which the adapted value is written or the mathematical expression thereof enables supply of fuel to an engine in an injection mode (injection pattern) suitable for an engine operating condition at each time even in a case of a multiple injection as in the case of a single stage injection (main injection only). However, inventors of the present invention have confirmed that in a case of performing a multiple injection by using such a controller, a control error with respect to a target engine operating condition becomes larger than in a case of a single stage injection, due to sequential injections performed at short intervals, For example, each of injections sequentially performed (particularly a sub-injection with a smaller quantity of fuel other than a main injection) is subject to various influences caused by performing an injection before or after that injection. One of them is an influence of an injection characteristic of the injector, and more particularly, of an individual difference thereof.
For example, in a case of mass production of each element in an engine control system for mass sales a certain degree of the individual difference usually occurs in characteristics of various control components including the injector between engines or even between cylinders in a case of a multi-cylinder engine. In a case of the mass production, determination of an adapted value (optimal injection pattern) of each element (for example, all cylinders mass-produced and mounted in a vehicle) in consideration of the individual difference thereof requires too much time and too many jobs in the present production system, and therefore, is not realistic. Therefore, even in a case of using the map in which the adapted value is written or the mathematical expression, it is difficult to perform a control considering all influences of the individual difference.
Further, the inventors of the present invention have confirmed that yet in a case of the aforementioned multiple injection unlike a case of the single stage injection, the injection characteristic concerning the multiple injection (plural sequential injections) is subject to influence of the individual difference, besides a usual injection characteristic. Accordingly, it is required to consider the injection characteristic of the multiple injection in addition to that of the single stage injection for obtaining an aimed engine operation condition through the multiple injection with high precision. Therefore, in conventional controllers including the controller described in the aforementioned Patent Document 1, it is difficult to perform control of the engine operation condition with high precision, particularly in a case where the controller is applied to control of the multiple injection.
In a case of performing injection control with high precision, a characteristic change due to aging of control components or the like can not be ignored. In conventional controllers including the controller described in the aforementioned Patent Document 1, even if an optimal value is obtained at an initial stage with high precision, the influence of the subsequent characteristic change can not be known. Therefore, a deviation from the optimal value possibly occurs with an elapse of time. In this case, there may be adopted a scheme of beforehand obtaining an adapted value of a degradation coefficient (coefficient relating to the degree of aging degradation) by an experiment value or the like to possess the adapted value as a map or a mathematical expression. However, since the aforementioned individual difference exists for each component even concerning such an aging characteristic change, it is difficult to completely eliminate the influence.